This invention relates to a pressure gauge in general, and more particularly to a device used in paper manufacturing, web press printing and paper coating which allows for a nondestructive, repeatable and consistent test for surface contamination.
The process of manufacturing paper involves combining various materials including wood pulp, filler, surface treatment chemicals, in an aqueous solution in a structure known as a head box. The aqueous solution is passed along a papermaking web as water is removed from the solution creating a solid paper film which may be further treated with coating chemicals or sizing chemicals in a structure known as the size press or coater. The film is eventually dried and wound on winders. In the newsprint and magazine industry, wounded rolls of paper for the printing process is then shipped to the printers for printing.
The problem arises when debris originating from the surface of the paper or paperboard contaminates the printing machines by depositing on the printing machines. Debris on the printing machines requires stopping the printing operation and cleaning the printing machines. The debris is caused by certain ones of the materials poorly binding to the surface of the sheet. These materials may include fiber and minerals which have been used as a low cost filler or fiber substitute and similar materials which were previously placed in the head box for providing the paper with strength and shininess. In printing operations, the debris causes problems such as contamination of the off-set print blanket, contamination of the printed image, and similar problems.
The contamination of printers is prevalent due to the increasing use of secondary pulp fibers and filler which are added to the pulp during papermaking to reduce cost and thus comply with contemporary marketing requirements. The secondary pulp fibers and filler are difficult to bind to the paper sheet surface typically causing higher levels of contamination problems during the printing operation.
Consequently, a need has arisen to reliably predict whether a sheet of paper or paperboard will deposit contamination either from fiber "linting" or mineral filler "dusting" during the printing operation. Generally contamination could only be evaluated during the performance of the printing operation which is generally too late and required the printing press to be shut down if contamination was too prevalent.
Previously, papermakers and printers, to detect the cleanliness of the paper sheet and thus the potential for contamination of the printing press, would apply a dark cloth to the surface of the sheet while the sheet was rotating on either the upwinder at the paper mill or the downwinder at the printer. By applying a cloth, by hand, to the sheet surface of the paper or paperboard, the propensity of the sheet to cause dusting or linting was roughly judged by observing the amount of debris accumulated on the cloth. The problem with this method is that the amount of pressure applied to the cloth and the time that the cloth is held against the sheet is inconsistent varying with the operator. This uncontrolled method of manually applying a sheet of dark cloth to the surface of the paper sheet produces inconsistent results depending on the operators and is inadequate.
Accordingly, it is an object of the present invention to provide a reliable method for testing the propensity of a roll of paper to cause dusting or linting during printing;
Also, it is an object of the present invention to provide a device that insures that a test cloth is pressed against a roll of paper at a controlled pressure for testing the propensity of the sheet to cause dusting or linting during printing;
Also, it is an object of the present invention to provide a dusting/surface contamination gauge which accurately and reliably indicates the application of a predetermined amount of pressure being applied to a test cloth;
Furthermore, it is an object of the present invention to provide a heavyduty dusting surface contamination gauge for industrial use.